Various techniques have been adopted for removing accumulated particulate matter from the surface of a filter element, in order to regenerate the filter.
Clapper, U.S. Pat. No. 4,299,245 discloses an ex-situ cleaning apparatus. The filter to be cleaned is removed, placed in the apparatus and sprayed with a cleaning solution via external and internal spray bars, while the filter is rotated. Another ex-situ filter cleaning apparatus is disclosed in Stuckey, U.S. Pat. No. 7,282,086 B2. A cleaning fluid is injected into the interior of the filter, while the filter is rotated, whereby the cleaning fluid is forced through the filter by centrifugal force.
Apparatus for in-situ cleaning of filters are disclosed in Dudley et al., U.S. Pat. No. 6,156,213 and Clary, U.S. Pat. No. 6,874,641 B2. Cleaning water is sprayed against the surface of the filter element, causing the filter element to rotate, during a regeneration step.
Benenson, Jr. et al., U.S. Pat. No. 6,861,004 B2 disclose a self-cleaning water filter employing a variety of cleaning techniques, including a reverse flow of clean water, a brush or scraper to dislodge accumulated particulate matter on the outer surface of the filter, and an ultrasonic generator suspended in the hollow interior of the filter. The ultrasonic generator may be activated during the cleaning step, when the clean water is flowing in reverse through the filter element.
Self-cleaning filter apparatus employing centrifugal force during an in-situ cleaning cycle are disclosed in the following references. Bergdahl, U.S. Pat. No. 4,130,404 discloses a fluid filter, which undergoes a cleaning cycle during which the flow of fluid is reversed while the filter is simultaneously spun at high speed. A cleaning fluid may be sprayed into the core of the filter element, while it is spun. Self-cleaning filter apparatus employing centrifugal force are also disclosed in Grotto, U.S. Pat. No. 4,222,755 and Dudley, U.S. Pat. No. 6,569,218 B2.
Another self-cleaning filter employing centrifugal force is disclosed in EP 0 993 853 A2. A series of disc filters are mounted on a shaft. During cleaning, the fluid flowing from the pump is diverted to the impeller of a vane turbine, which in turn causes the shaft to rotate. The centrifugal force generated by rotation of the shaft detaches sediment from the surface of the disc filters.
Self-cleaning filters in which particulate matter filtered from a fluid stream collects on the inside of the filter element are disclosed in Caracciolo, Jr., U.S. Pat. No. 5,855,794 and Shiekelmacher, US 2008/0047885 A1. During the cleaning step, the filter is backwashed, while cleaning heads traverse the inside of the filter element to remove collected particulate matter.
Despite the attempts to develop methods and apparatus for cleaning filters, there remains a need for a self-cleaning filter with improved performance, while conserving resources and energy.